It is known from U.S. Pat. No. 4,955,989 to convey bulk materials from a lower pressure container to a higher-pressure container by means of a lock hopper. Such a lock hopper system is commercially used to bring a solid fuel, for example coal, to the same elevated pressure as the pressure of an entrained flow gasification reactor. In the reactor the solid fuel is partially oxidized to a mixture of carbon monoxide and hydrogen.
A disadvantage of such a lock hopper system is that it involves many process handling operations, like opening of valves, pressurizing sluice vessels, emptying sluice vessels and the like. The process as a consequence also involves a complicated process control. There is thus a desire to simplify this system.
A possible solution to simplify the lock hopper system is to use a bulk materials pump. The use of such a pump is advantageous because the solids are brought to the higher-pressure environment in a continuous manner, thereby avoiding the above-described handling of the lock hopper system. Many bulk material pumps have been suggested for this use of which some examples are described in EP-A-015037, U.S. Pat. No. 4,120,410 and U.S. Pat. No. 4,605,352. Although these apparatuses have their specific advantages none of them have actually been successfully developed commercially. Most likely because they are complex and/or involve a high-energy input.
In a more recent publication, U.S. Pat. No. 5,355,993, a bulk material pump is described wherein the bulk material pump has a pair of rotatable disk members arranged coaxial and spaced away from each other. The disk members are arranged in a peripheral wall having an inlet and outlet for bulk material. In use the material as supplied at the inlet is caught between the disks and transported to the outlet end. A scraper positioned between the disks avoids material returning to the inlet. The disk may be tilted with respect to each other resulting in that the distance between said disks at the inlet is greater than the distance between said disks at the outlet.
Although the materials pump of U.S. Pat. No. 5,355,993 has specific advantages over the earlier designs some disadvantages, like a high-energy consumption, are still present which do not allow direct application in a process to transport material from a lower pressure environment to a higher-pressure environment.
It would be advantageous to provide a bulk material pump having a lower energy consumption.